Stubborn foam and paint stains on old brick

[simply_sam]

I replaced an old entry door on an old brick house and now the owner wants me to completely clean the brick where the old wooden trim was. The brick is red, but it has patches of old white paint and some residue from cured expansion foam that has been there for years. I tried several things already like acetone and some diluted muriatic acid with a stiff brush, but nothing seems to get the residue off. And to make things worse, using my hard, stiff brush leaves a grayish mark where I scrubbed the brick. I need to find something strong enough to dissolve that old foam and paint without damaging the porous brick face. What chemicals or specialized masonry cleaners work best on a job this old and how can I clean this brick without leaving that permanent gray tint behind? Any ideas will be helpful.

 

[bigbitez]

To get rid of foam residue, you can use something like xylene or a polyurethane remover. But make sure to apply it carefully and rinse it well. Skip the stiff wire brushes since they’ll scratch the surface. It is best to use nylon bristles or a plastic scraper instead to lift the softened gunk.